DATA MANAGEMENT MBF3C Lesson #3: Display Data

Learning Goals: To identify different types of one-variable data (i.e., categorical, discrete, continuous) To graph the data by hand To graph the data with the TI-83

Introduction You have heard the saying “a picture is worth a thousand words.” The same can be said about a graph. A graph is a visual representation of data that displays the relationship among the variables. Graphs can summarize data, and present data more clearly and concisely than a table or written text.

Bar Graph and Circle Graph (p. 118) Jong has a part-time job at a music store. The table shows Jong’s expenses last month.

2. Copy and complete the table. Calculate the percent and angle measure for each expense. Create a circle graph to represent the data. Include a title for the graph and label the sectors Entertainment Clothing Cell Phone Lunch Transport Rent TOTAL

OPEN UP MICROSOFT EXCEL ON YOUR COMPUTER TURN TO PAGE 119

Create a Histogram (p. 121)

Interpret a Bar Graph (p. 123) Colleen surveyed the students at her school about their favourite sports. She chose a bar graph to display her results. Use the bar graph to answer each question.

Interpret a Bar Graph (p. 123) a) Which sport is the most popular? ANSWER: The tallest bar is for hockey. Hockey is the most popular sport. b) Which sport is the least popular? ANSWER: The shortest bar is for golf. Golf is the least popular sport. c) Does your answer to part b) mean that students do not like this sport? Explain. ANSWER: No. Colleen’s survey asked students about the sports they liked, not the sports they disliked. d) How many students said that volleyball was their favourite sport? ANSWER: Fifteen students said that volleyball was their favourite sport. e) How many students participated in Colleen’s survey? ANSWER: = 146

Analyze Continuous Data (p. 124) The histogram shows the masses of a sample of patients at a hospital. a) How many patients have a mass of at least 85 kg but less than 90 kg? Answer: The bar with left side 85 and right side 90 represents the number of patients who have a mass in the interval [85–90). The height of the bar is 13; therefore, 13 patients have a mass of at least 85 kg but less than 90 kg. b) How many patients have a mass of at least 100 kg? Answer: Two patients have a mass in the interval [100–105) and two patients have a mass in the interval [105–110). So, four patients have a mass of at least 100 kg. c) How many patients are in the sample? Answer: = 79 d) Find the percent of patients who have a mass of at least 100 kg.

Colleen surveyed the students at her school about their favourite sports. She chose a bar graph to display her results. Use the bar graph to answer each question.

The data relating to Jong’s expenses are categorical data. The entries in the first column of the table are non-numerical—they are categories. There are two types of data. Data that can have any numerical value are continuous data Data that can only have certain values within a given range are discrete data. You can use a histogram to display continuous data.

TYPES OF DATA (p. 120) categorical data data that are types rather than numbers; for example: colours, types of snack foods continuous data data that can have any numerical value within a finite or infinite interval; for example: the heights of students in your class discrete data data that are distinct and can be counted; for example: the number of students who like rice

Design a Survey Question (p. 110) 6.Reflect People sometimes might not answer a survey question according to their own viewpoint if the nature of the question, or the way the question is asked, influences their opinion. This response bias produces inaccurate survey results. Study your own question and your partner’s question. Discuss the way each question is written and decide if the question may result in response bias.

Primary versus Secondary Research When you conduct a survey or perform an experiment, you are the primary source of the data. When you work with data from the Internet, published materials, or Statistics Canada, you are using a secondary source.

Response Bias (p. 112) A parent council survey is conducted to learn if an after-school music program should be offered. The survey question reads: Early musical training helps develop brain areas involved in language and reasoning. Should the school offer an after-school music program? a) Explain why this question may result in response bias. By stating an opinion about music training in the first sentence, before asking the question, the survey makes it clear that the parent council wants a positive answer. b) Rewrite the question to eliminate possible response bias. A possible question might be: Would you enrol your child in an after-school music program?

Measurement Bias (p. 112) Andre wrote this survey question: Who do you think is the best female tennis player of all time? a) Martina Navratilova b) Chris Evert c) Billie Jean King d) Serena Williams e) Other: Identify any weaknesses in this survey ANSWER: By naming specific players, the survey influences the respondents’ answers. Respondents might not take the time to fill in the “Other” selection and might randomly select a player or simply choose a name they recognise. This measurement bias might cause an exaggeration or an underestimation of the results for the population.

Non-Response Bias (p. 113) At a new restaurant, wait staff ask every fifth customer to answer a questionnaire about food quality and service once they have finished their meal. About 30% of customers surveyed fill out the questionnaire. The majority of customers who fill out the questionnaire complain about poor service. The restaurant manager concludes that the wait staff need more training. Is her conclusion reasonable? ANSWER: The conclusion is not reasonable because only 30% of those surveyed answered the questionnaire. Customers who did respond might have done so because they were unhappy with the service. Those who were happy with the service might have simply ignored the questionnaire because the service did not need to be improved. This non-response bias leads to inaccurate results because only a small number of people in the sample respond.

Key Concepts from this Lesson Someone who collects data for their own use is a primary source. A database or research collected by someone else is a secondary source. Bias is an intentional or unintentional distortion of the data collected in a survey. A survey should be as free of bias as possible. Three types of bias were discussed: response, measurement & non-response.

ISU, Review Part A Question 19: Any survey that asks people to return their completed questionnaires by mail is subject to: a. Response Bias b. Non-Response Bias c. Sampling Biasd. d. No bias at all

ISU, Review Part B Question 33: Classify the data coming from each of the following as primary or secondary research a.A survey of students in your school Primary Secondary b.An internet search to find information Primary Secondary c.A phone calls made to residential homes Primary Secondary d.Data given to you that your teacher collected Primary Secondary

ISU, Review Part B Question 34: Classify the data coming from each of the following as Bias or Not Bias. a.A survey of students in your school Bias Not Bias b.An internet search to find information Bias Not Bias c.A phone calls made to residential homes Bias Not Bias d.Data given to you that your teacher collected Bias Not Bias

ISU, Review Part C Question 7: The following were questions asked in a survey. Explain why the question is bias. a) The government has been underfunding the arts for years. Should the government increase funding for the Ontario Art Gallery? b) Please select your favourite type of television show: A.Sports B.Reality Show C.Crime Drama D.Other _____ (please specify)